Top government executives could be rewarded with yearly bonuses worth between $1,200 and $9,500 under a tentative legislative proposal being considered by Carter aides.

The idea of bonuses ranging from 3 percent to 20 percent of salary for top-paid career and political appointees is contingent on the president approving, and Congress approving, a new Senior Executive Service for federal supergraders.

Under the SES plan, part of an overall bureaucratic "reform" package being worked up for Carter, about 9,000 key workers in Grades 16 through 18, and some top executives, would be converted to SES status.

The SES plan would drop grades for personnel, in favor of a rank-in-person system similar to the military or the Foreign Service. Incumbent supergraders, who voluntarily entered the SES, would have pay set according to their abilities, as determined by their agency. They would serve wherever needed, and could be bounced back to Grade 15 if they didn't work out.

New executives coming into government or promoted into the executive levels would be required to join the SES. It would provide more opportunities - and greater job risks - than the present supergrade system.

In addition to bonuses for top officials, another concept being considered by the Civil Service Commission and the Office of Management and Budget would set up a somewhat similar reward system for more than 150,000 middle-level managers. Under that proposal, which has not yet been cleared or sent to the president, some managers would also get annual bonuses although the percentage amounts would be less than those for top executives.

Federal officials stress that the ideas haven't been cleared by CSC and OMB brass who are studying a comprehensive package that proposes major changes in the way government workers are hired, motivated, promoted, paid and fired. Those proposals, from the Personnel Management Project (part of the president's reorganization task force), will form part of the base from which CSC-OMB will draft a set of legislative and administrative reforms for the president.

Insiders believe the president will approve the SES concept. They say the president likes the idea of incentive pay for top managers, but has not yet decided what form the package will take. When it goes to Congress, they say, it will represent his ideas for reshaping the federal establishment.

The proposal to give bonuses to mid-level managers is less certain than the SES plan, officials believe. It involves many more people and would also cost more money. Also, they say, the key to it is to have a balancing "disincentive" that would prevent managers from "coasting" along in the knowledge that they would get regular pay rises anyhow simply for performing satisfactorily.

Officials expect the government reorganization draft proposals will be sent the president shortly (he has already tentatively approved some portions) and that his version could go to Congress by late February.